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Apache Pekko/org.apache.pekko.cluster.ddata/GCounter

GCounter

org.apache.pekko.cluster.ddata.GCounter
See theGCounter companion object
final class GCounter extends DeltaReplicatedData, ReplicatedDelta, ReplicatedDataSerialization, RemovedNodePruning

Implements a 'Growing Counter' CRDT, also called a 'G-Counter'.

It is described in the paper A comprehensive study of Convergent and Commutative Replicated Data Types.

A G-Counter is a increment-only counter (inspired by vector clocks) in which only increment and merge are possible. Incrementing the counter adds 1 to the count for the current node. Divergent histories are resolved by taking the maximum count for each node (like a vector clock merge). The value of the counter is the sum of all node counts.

This class is immutable, i.e. "modifying" methods return a new instance.

Attributes

Companion
object
Source
GCounter.scala
Graph
Supertypes
trait Serializable
class Object
trait Matchable
class Any
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Members list

Type members

Types

type D = GCounter

The type of the delta. To be specified by subclass. It may be the same type as T or a different type if needed. For example GSet uses the same type and ORSet uses different types.

The type of the delta. To be specified by subclass. It may be the same type as T or a different type if needed. For example GSet uses the same type and ORSet uses different types.

Attributes

Source
GCounter.scala
type T = GCounter

The type of the concrete implementation, e.g. GSet[A]. To be specified by subclass.

The type of the concrete implementation, e.g. GSet[A]. To be specified by subclass.

Attributes

Source
GCounter.scala

Value members

Concrete methods

def :+(n: Long)(implicit node: SelfUniqueAddress): GCounter

Increment the counter with the delta n specified. The delta must be zero or positive.

Increment the counter with the delta n specified. The delta must be zero or positive.

Attributes

Source
GCounter.scala
override def equals(o: Any): Boolean

Compares the receiver object (this) with the argument object (that) for equivalence.

Compares the receiver object (this) with the argument object (that) for equivalence.

Any implementation of this method should be an equivalence relation:

  • It is reflexive: for any instance x of type Any, x.equals(x) should return true.
  • It is symmetric: for any instances x and y of type Any, x.equals(y) should return true if and only if y.equals(x) returns true.
  • It is transitive: for any instances x, y, and z of type Any if x.equals(y) returns true and y.equals(z) returns true, then x.equals(z) should return true.

If you override this method, you should verify that your implementation remains an equivalence relation. Additionally, when overriding this method it is usually necessary to override hashCode to ensure that objects which are "equal" (o1.equals(o2) returns true) hash to the same scala.Int. (o1.hashCode.equals(o2.hashCode)).

Value parameters

that

the object to compare against this object for equality.

Attributes

Returns

true if the receiver object is equivalent to the argument; false otherwise.

Definition Classes
Any
Source
GCounter.scala
def getValue: BigInteger

Java API: Current total value of the counter.

Java API: Current total value of the counter.

Attributes

Source
GCounter.scala
override def hashCode: Int

Calculate a hash code value for the object.

Calculate a hash code value for the object.

The default hashing algorithm is platform dependent.

Note that it is allowed for two objects to have identical hash codes (o1.hashCode.equals(o2.hashCode)) yet not be equal (o1.equals(o2) returns false). A degenerate implementation could always return 0. However, it is required that if two objects are equal (o1.equals(o2) returns true) that they have identical hash codes (o1.hashCode.equals(o2.hashCode)). Therefore, when overriding this method, be sure to verify that the behavior is consistent with the equals method.

Attributes

Returns

the hash code value for this object.

Definition Classes
Any
Source
GCounter.scala
def increment(node: SelfUniqueAddress, n: Long): GCounter

Increment the counter with the delta n specified. The delta n must be zero or positive.

Increment the counter with the delta n specified. The delta n must be zero or positive.

Attributes

Source
GCounter.scala
override def merge(that: GCounter): GCounter

Monotonic merge function.

Monotonic merge function.

Attributes

Definition Classes
Source
GCounter.scala
override def mergeDelta(thatDelta: GCounter): GCounter

When delta is merged into the full state this method is used. When the type D of the delta is of the same type as the full state T this method can be implemented by delegating to merge.

When delta is merged into the full state this method is used. When the type D of the delta is of the same type as the full state T this method can be implemented by delegating to merge.

Attributes

Definition Classes
Source
GCounter.scala
override def modifiedByNodes: Set[UniqueAddress]

The nodes that have changed the state for this data and would need pruning when such node is no longer part of the cluster.

The nodes that have changed the state for this data and would need pruning when such node is no longer part of the cluster.

Attributes

Definition Classes
Source
GCounter.scala
override def needPruningFrom(removedNode: UniqueAddress): Boolean

Does it have any state changes from a specific node, which has been removed from the cluster.

Does it have any state changes from a specific node, which has been removed from the cluster.

Attributes

Definition Classes
Source
GCounter.scala
override def prune(removedNode: UniqueAddress, collapseInto: UniqueAddress): GCounter

When the removed node has been removed from the cluster the state changes from that node will be pruned by collapsing the data entries to another node.

When the removed node has been removed from the cluster the state changes from that node will be pruned by collapsing the data entries to another node.

Attributes

Definition Classes
Source
GCounter.scala
override def pruningCleanup(removedNode: UniqueAddress): GCounter

Remove data entries from a node that has been removed from the cluster and already been pruned.

Remove data entries from a node that has been removed from the cluster and already been pruned.

Attributes

Definition Classes
Source
GCounter.scala
override def resetDelta: GCounter

Reset collection of deltas from mutator operations. When the Replicator invokes the modify function of the Update message the delta is always "reset" and when the user code is invoking one or more mutator operations the data is collecting the delta of the operations and makes it available for the Replicator with the delta accessor. When the Replicator has grabbed the delta it will invoke this method to get a clean data instance without the delta.

Reset collection of deltas from mutator operations. When the Replicator invokes the modify function of the Update message the delta is always "reset" and when the user code is invoking one or more mutator operations the data is collecting the delta of the operations and makes it available for the Replicator with the delta accessor. When the Replicator has grabbed the delta it will invoke this method to get a clean data instance without the delta.

Attributes

Definition Classes
Source
GCounter.scala
override def toString: String

Returns a string representation of the object.

Returns a string representation of the object.

The default representation is platform dependent.

Attributes

Returns

a string representation of the object.

Definition Classes
Any
Source
GCounter.scala
def value: BigInt

Scala API: Current total value of the counter.

Scala API: Current total value of the counter.

Attributes

Source
GCounter.scala
override def zero: GCounter

The empty full state. This is used when a delta is received and no existing full state exists on the receiving side. Then the delta is merged into the zero to create the initial full state.

The empty full state. This is used when a delta is received and no existing full state exists on the receiving side. Then the delta is merged into the zero to create the initial full state.

Attributes

Definition Classes
Source
GCounter.scala

Deprecated methods

def +(n: Long)(implicit node: Cluster): GCounter

Attributes

Deprecated
[Since version Akka 2.5.20]
Source
GCounter.scala
def increment(node: Cluster, n: Long): GCounter

Attributes

Deprecated
[Since version Akka 2.5.20]
Source
GCounter.scala

Concrete fields

override val delta: Option[GCounter]

The accumulated delta of mutator operations since previous resetDelta. When the Replicator invokes the modify function of the Update message and the user code is invoking one or more mutator operations the data is collecting the delta of the operations and makes it available for the Replicator with the delta accessor. The modify function shall still return the full state in the same way as ReplicatedData without support for deltas.

The accumulated delta of mutator operations since previous resetDelta. When the Replicator invokes the modify function of the Update message and the user code is invoking one or more mutator operations the data is collecting the delta of the operations and makes it available for the Replicator with the delta accessor. The modify function shall still return the full state in the same way as ReplicatedData without support for deltas.

Attributes

Source
GCounter.scala
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